Liquid crystal compounds exhibiting negative anisotropy of...

Details Liquid crystal compounds exhibiting negative anisotropy of... Liquid crystal compounds exhibiting negative anisotropy of...

1999-05-28

2001-04-03

Wu, Shean C. (Department: 1756)

Stock material or miscellaneous articles

Liquid crystal optical display having layer of specified...

C252S299010, C252S299610, C252S299630, C252S299660, C570S127000, C570S129000

Reexamination Certificate

active

06210761

ABSTRACT:

TECHNICAL FIELD
The present invention relates to novel liquid crystalline compounds and liquid crystal compositions. More specifically, it relates to liquid crystalline compounds having a fluorine substituted-1,4-phenylene group, liquid crystal compositions comprising the compound, and liquid crystal display devices fabricated by using the liquid crystal composition.
BACKGROUND ART
Display devices comprising liquid crystalline compounds (the term “liquid crystalline compounds” is used in this specification as a general term for the compounds which exhibit a liquid crystal phase and for the compounds which do not exhibit a liquid crystal phase but are useful as a component of liquid crystal compositions) have widely been utilized for the display of watches, tabletop calculators, word processors, or the likes. In connection with the display devices, researches on in-plane switching (IPS) mode and vertical alignment (VA) mode by which characteristics of viewing angle can be improved at a low manufacturing cost are extensively conducted in recent years.
In liquid crystal compositions for the IPS mode or VA mode, those having a negative dielectric anisotropy value are preferable, and such physical properties as a high voltage holding ratio, low threshold voltage, their small temperature dependency, wide temperature range of liquid crystal phase, excellent miscibility with other liquid crystal materials, and low viscosity are sought for the compositions.
As a component of such liquid crystal compositions, many liquid crystalline compounds in which fluorine atom substituted at their lateral position were investigated and, for example, the following compounds are disclosed in the literatures.
However, they have such problems that the compounds of 1) are high in threshold voltage and that the compounds of 2) and 3) are low in transition temperature to isotropic phase or tend to exhibit smectic phase, and thus the compounds of 2) and 3) hardly from a stable nematic phase particularly at low temperatures when used as component of liquid crystal compositions.
DISCLOSURE OF THE INVENTION
In view of such characteristics required of liquid crystal compositions as described above, an object of the present invention is to provide liquid crystalline compounds which exhibit a negative dielectric anisotropy value, have an extremely high voltage holding ratio and a low threshold voltage, are remarkably small in their dependency on temperature, hardly exhibit smectic phase, and are excellent in miscibility with other liquid crystal materials; to provide liquid crystal compositions comprising the liquid crystalline compound; and to provide liquid crystal display devices fabricated by using the liquid crystal composition.
As a result of diligent investigation by the present inventors to solve the subjects described above, it has been found that
[1] the liquid crystalline compounds expressed by the general formula (1)
wherein Ra and Rb independently represent a straight chain or branched alkyl group having 1 to 20 carbon atoms in which alkyl group any non-adjacent methylene group (—CH
2
—) may be replaced by oxygen atom; Y
1
, Y
2
, Y
3
, Y
4
, Y
5
, and Y
6
each independently represent hydrogen atom or fluorine atom provided that at least three of Y
1
, Y
2
, Y
3
, Y
4
, Y
5
, and Y
6
represent fluorine atom; Z
1
and Z
2
each independently represent —(CH
2
)
2
—, —(CH
2
)
4
—, —CH
2
O—, —(CH
2
)
3
O—, or single bond provided that in no case represent Z
1
and Z
2
simultaneously single bond; and any atom which constitutes the compound may be replaced by its isotope, have expected properties, leading to the accomplichment of the present invention.
Also, the present invention has the following aspects:
[2] The liquid crystalline compound recited in aspect [1] above wherein at least one of Z
1
and Z
2
is —(CH
2
)
2
— or —CH
2
O—.
[3] A liquid crystal composition comprising at least one liquid crystalline compound recited in claim aspect [1] or [2] above.
[4] A liquid crystal composition comprising, as a first component, at least one liquid crystalline compound recited in aspect [1] or [2] above, and comprising, as a second component, at least one compound selected from the group consisting of the compounds expressed by any one of the general formulas (2), (3) and (4)
wherein R
1
represents an alkyl group having 1 to 10 carbon atoms in which alkyl group any non-adjacent methylene group may be replaced by oxygen atom or —CH═CH—, and any hydrogen atom in which alkyl group may be replaced by fluorine atom; X
1
represents fluorine atom, chlorine atom, —OCF
3
, —OCF
2
H, —CF
3
, —CF
2
H, —CFH
2
, —OCF
2
CF
2
H or —OCF
2
CFHCF
3
; L
1
and L
2
each independently represent hydrogen atom or fluorine atom; Z
4
and Z
5
each independently represent —(CH
2
)
2
—, —(CH
2
)
4
—, —COO—, —CF
2
O—, —OCF
2
—, —CH═CH— or single bond; ring B represents 1,4-phenylene in which hydrogen atom may be replaced by fluorine atom, trans-1,4-cyclohexylene or 1,3-dioxane-2,5-diyl; ring C represents trans-1,4-cyclohexylene or 1,4-phenylene in which phenylene hydrogen atom may be replaced by fluorine atom; and any atom which constitutes these compounds may be replaced by its isotope.
[5] A liquid crystal composition comprising, as a first component, at least one liquid crystalline compound recited in aspect [1] or [2] above, and comprising, as a second component, at least one compound selected from the group consisting of the compounds expressed by the general formula (5) or (6)
wherein R
2
and R
3
each independently represent an alkyl group having 1 to 10 carbon atoms in which alkyl group any non-adjacent methylene group may be replaced by oxygen atom or —CH═CH, and any hydrogen atom in which alkyl group may be replaced by fluorine atom; X
2
represents —CN group or —C≡C—CN; ring D represents trans-1,4-cyclohexylene, 1,4-phenylene, 1,3-dioxane-2,5-diyl or pyrimidine-2,5-diyl; ring E represents 1,4-phenylene in which hydrogen atom may be replaced by fluorine atom, trans-1,4-cyclohexylene or pyrimidine-2,5-diyl; ring F represents trans-1,4-cyclohexylene or 1,4-phenylene; Z
6
represents —(CH
2
)
2
—, —COO— or single bond; L
3
, L
4
and L
5
each independently represent hydrogen atom or fluorine atom; b, c and d are each independently 0 or 1; and any atom which constitutes these compounds may be replaced by its isotope.
[6] A liquid crystal composition comprising, as a first component, at least one liquid crystalline compound recited in aspect [1] or [2] above, comprising, as a second component, at least one compound selected from the group consisting of the compounds expressed by any one of the general formulas (2), (3) and (4) described above, and comprising, as a third component, at least one compound selected from the group consisting of the compounds expressed by any one of the general formula (7), (8) and (9)
wherein R
4
and R
5
each independently represent an alkyl group having 1 to 10 carbon atoms in which alkyl group any non-adjacent methylene group may be replaced by oxygen atom or —CH═CH—, and any hydrogen atom in which alkyl group may be replaced by fluorine atom; ring G, ring I and ring J each independently represent 1,4-phenylene in which hydrogen atom may be replaced by fluorine atom, trans-1,4-cyclohexylene or pyrimidine-2,5-diyl; Z
7
and Z
8
independently represent —C≡C—, —COO—, —(CH
2
)
2
—, —CH═CH— or single bond; and any atom which constitutes these compounds may be replaced by its isotope.
[7] A liquid crystal composition comprising, as a first component, at least one liquid crystalline compound recited in aspect [1] or [2] above, comprising, as a second component, at least one compound selected from the group consisting of the compounds expressed by the general formula (5) or (6) described above, and comprising, as a third component, at least one compound selected from the group c

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